The invention relates to a reconfigurable switch matrix in particular for space applications.
For applications that require high reliability, it is common practice to provide redundant electronic elements so that in the event of one of them breaking down, it can be replaced by an identical element. This problem arises in particular for space applications.
To enable a spare element to replace the element that has broken down, it is necessary to provide switching which is controlled either automatically or remotely.
In general, such switching is provided by a matrix having n inlets and p outlets, where the number p of outlets is greater than the number n of inlets. Each of the inlets delivers a signal to an element connected to a corresponding outlet. Thus, only n out of the p possible outlets are normally active. When the element connected to one of the outlets breaks down, then switching is performed so that the corresponding inlet is connected to an outlet having a replacement element connected thereto.
The switch matrices that have been used in the past make use of mechanical switches.
An electronic type replacement configuration has yet to be developed that offers advantages comparable to those of mechanical switch matrices. Mechanical matrices give rise to negligible attenuation of about 0.15 dB, while electronic switches lead to greater losses or attenuation of about 1.5 dB. The greater losses do not, in themselves, constitute an obstacle to the use of electronic switches, since said electronic switches make it possible for bulk, mass, and prices to be significantly lower than the bulk, mass, and prices of matrices having mechanical type elements. However, it has been found that if each mechanical switch in a switch matrix of the mechanical type is replaced by an electronic switch, then when switching is performed to replace a faulty element with a spare element, the losses due to the matrix itself are generally not the same before and after switching.
To remedy that drawback, it is necessary to provide in each spare branch, a variable gain amplifier enabling the various amounts of attenuation to be compensated. However, that solution is difficult and expensive to implement.
To resolve that problem, the switch matrix of the invention includes a plurality of switch members of the electronic type which are mounted in such a manner that when an inlet of one outlet is switched to another outlet, the losses due to the electronic switch members passed through remain at substantially the same value.
It is thus not necessary to provide variable gain amplification to compensate the various losses between the paths passing through in the matrix, since it is the structure proper of said matrix which enables said compensation.
In an embodiment, in which each inlet is for connection to r outlets, each inlet is provided with a set of switch members associated so as to present one inlet and r outlets. In that case, it is preferable to provide, for each outlet a set of switch members mounted the opposite way round to the inlet members, said set having r inlets and one outlet; the sets associated with the outlets are preferably of structure analogous or identical (but symmetrical) to the structure of the sets associated with the inlets.
The switch members are, for example monolithic microwave integrated circuit (MMIC) technology switches with two or three outlets and presenting losses limited to about 1.5 dB.
The present invention provides a switch matrix having n inlets and p outlets, p being greater n, the matrix including a plurality of switch members each having one inlet and at least two outlets and each enabling a signal applied to the inlet of said member to be transferred to one of the outlets, each inlet of the matrix being for connection to one out of r outlets. The switch members are of the electronic type and are mounted in such as manner that when switching is performed consisting in modifying a connection from an inlet of the matrix to an outlet thereof, so that said same inlet is connected to another outlet of the matrix, the losses due to the switch members passed through remain at substantially the same value.
In an embodiment, the matrix comprises, for each inlet, a set of switch members associated so as to present one inlet and r outlets.
In an embodiment, the matrix comprises, for each outlet, a set of switch members having r inlets and one outlet, the sets associated with the outlets being mounted the opposite way round to the sets associated with the inlets.
In an embodiment, the sets associated with the outlets are of structure analogous to the structure of the sets associated with the inlets.
In an embodiment, the electronic switches are microwave range integrated circuits.
The present invention also provides use of a matrix in replacing a faulty electronic element connected to an outlet of the matrix, with another element connected to another outlet of the matrix.